The present invention relates to a plane film cassette for receiving at least one film. More particularly, it relates to a plane film cassette which has an illumination window at one of its sides, and a light-protective plate insertable into a slot of the cassette so as to cover the film in the cassette in light-tight manner.
Plane film cassettes of the above mentioned general type, which are designed for receiving two films and have two illuminating windows with light-protective plates, are disclosed for example in U.S. Pat. No. 3,373,673. In this cassette the required light-tightness in the slot for insertion of the light-protective plate from the interior of the cassette is performed by a plurality of elastic fingers which press from the interior of the cassette outwardly onto the light-protective plate when the latter is in the slot, or onto the cassette outer part when the light-protective plate is withdrawn from the slot. These fingers are coated with throughgoing strips of velvet for light-tightness. The disadvantage of such cassette is that, particularly for cassettes of large format or cassettes of relatively soft material such as synthetic plastic, the center of the cassette in the slot region is pressed through or bulged. Thereby the abutment of the strips over the entire width of the slot is no longer guaranteed, and light can penetrate into the interior of the cassette and expose the film.